It is known to chamfer glass panes, particularly for windshields and rear windows of motor vehicles, at the edges thereby, so that, first, a pane arranged horizontally on a conveyor device, for example, on a roller conveyor, is conveyed to a first cutting or trimming machine. As soon as the pane reaches the region of the first edge cutting machine, it is engaged by guide devices which are arranged, as seen in the conveying direction, on both sides of the cutting machine and is passed alongside of peripheral cutting wheels which are also arranged on each side of the cutting machine and is worked during this procedure. After leaving the first cutting machine, the glass pane is conveyed from the conveying device to a turnstile and is turned by 180.degree. in the turnstile. Subsequently, in this turned position, the pane is conveyed to a second edge cutting machine which corresponds to the first cutting machine and, consequently, the second cutting machine works the longitudinal edges of the glass pane. The peripheral cutting wheels used in both cutting machines have concave peripheral surfaces, as they are known from cutting wheels which are used for cutting C-shaped edges of panes for motor vehicles. In order to facilitate a high throughput and, in addition, to prevent an excessive wear of the expensive peripheral cutting wheels in the above-described edge cutting machine, the edges of the panes are chamfered in such a manner that the C-shape of the peripheral surface of the cutting wheel completely surrounds the entire edge region of the glass pane. The cutting wheel surface comes only into contact with the upper and lower edge of the glass pane and, thus, carries out a chamfering without working the end faces.
Because the end faces are not worked in the known edge cutting machines for chamfering glass panes, a rough surface remains which leads to undesirable hairline fractures during subsequent working steps, for example, during the production of laminated glass panes or particularly also during hardening of the glass panes. These hairline fractures may easily lead to a rupture of the glass panes. In particular, the above-described known edge cutting machine has the disadvantage that, due to a lacking force guidance of the peripheral cutting wheels which are arranged at the sides of the glass panes to be worked and are only loaded by weight or a spring, the corners of the panes which are, as a rule, essentially of rectangular design and have a very small radius of curvature, are worked only insufficiently. This leads to irregularities in the corner region which may later, namely during hardening of the glass panes, lead to cracks and, thus, to phenomena of failure. However, these disadvantages were put up with thus far, since the know double or twin edge cutting machine allows a high throughput. This is so because the glass pane, after cutting the longitudinal edges in the first edge cutting machine, can be conveyed without interruption into the second working station and, simultaneously to this procedure, the first edge cutting machine is loaded with a new pane to be worked. Accordingly, the sequence of conveying is not interrupted at all, not even during the cutting procedure.
On the other hand, from the German Auslegeschrift No. 2,349,871, a glass cutting machine of the above mentioned type is already known which serves particularly for cutting the C-shaped edges of glass panes for side windows and models of motor vehicles. In this case, the loading and unloading device has a support device or girder which is pivotally supported at a swivel arm which also has a rotary drive. At the free end of the girder there is provided a holding device for a glass pane. With respect to the axis of rotation of the rotary table, the swivel arm is arranged coaxially, while the girder is arranged in its center. As a result, the girder has two free ends, at each of which a holding device is arranged. The coaxial arrangement of the axis of rotation of the swivel arm relative to the axis of rotation of the rotary table prevents any relative movement between the holding devices and the gripping devices during loading or unloading.
In principle, the glass cutting or trimming machine according to the German Auslegeschrift No. 2,349,871 has been proven to be quite effective as far as the cutting of the C-shaped edges of relatively small glass panes is concerned. However, it has become apparent that it is difficult to use the known, automatically operating glass cutting machine of the indicated type for chamfering larger glass panes, particularly glass panes for front and rear windows, since the desired high throughput cannot be achieved in this case. This is due to the fact that the panes for front and rear windows have significantly larger dimensions than the panes for side windows of motor vehicles, so that, while maintaining manageable dimensions of the rotary table, it is not possible to simultaneously place two panes on the rotary table and work on them, as it is possible in the case of glass panes for side windows or models. On the contrary, in the known glass cutting machine it is only possible to always place a single front or rear window pane on the rotary table, so that significant time losses occur when the known glass cutting machine is used with the loading and unloading devices provided for this machine. These time losses inevitably lead to an accumulation when the conveying sequence remains unchanged. When front or rear window panes are cut or chamfered, by means of the loading and unloading device of the glass cutting machine according to the German Auslegeschrift No. 2,349,871, it is not possible at all to simultaneously place a new glass pane on the rotary table and to discharge an already worked pane.